Month: October 2015

We all know what comes out of the bottom of thunderstorms: lightning bolts. But on Oct. 20th, Thomas Ashcraft of New Mexico saw something coming out of the top. “I captured a form of a transient luminous event called a ‘blue starter’ shooting up from the top of a thunderstorm cloud,” he says. “Blue starters are rarely captured from ground level and there are hardly any specimens on the internet.”

Lightning scientist Oscar van der Velde explains this phenomenon: “A blue starter is an electric streamer discharge coming out of the top of a thundercloud, fanning out and reaching up to the stratosphere as high as 26 km altitude. First reported by UAF scientists Wescott and Sentman in 1995/1996, they were found to be different from blue jets, which reach 35-40 km height.”

“Since then, there have been very few reports of blue starters,” continues van der Velde. “It seems that unusual physical circumstances may be required to produce them. Also, geometry can prevent people from seeing blue starters when a cloud is nearby because the underbody of the cloud can block their view. At larger distances the blue/violet light does not make it to the observer due to scattering.”

Blue starters and blue jets are cousins of sprites, another form of exotic lightning that shoots up instead of down. Sprites, however, are more frequently observed. Check them out in the realtime photo gallery:

On the evening of Sept. 27th, Spaceweather.com and the students of Earth to Sky Calculus conducted a routine flight of their cosmic ray payload to the stratosphere. Routine, that is, except for one thing: the balloon flew at night during a lunar eclipse. One of the goals of the flight was to compare radiation levels at night to those recorded during the day. Here are the data they recorded:

Compare this plot of radiation vs. altitude to a similar plot recorded in broad daylight only a few days earlier. They are almost identical. Radiation levels in the stratosphere matched at the 1% level. Radiation levels at aviation altitudes (where planes fly) agreed within about 3%. Night and day were the same.

This simple experiment highlights something that is already well known to researchers. Cosmic rays in Earth’s atmosphere come mainly from deep space. They are accelerated toward Earth by supernovas, colliding neutron stars, and other violent events in the Milky Way. Flying at night is no safeguard against these energetic particles because they are ever-present, coming at us from all directions, day and night.

HEY THANKS (and Happy Birthday): The lunar eclipse flight was sponsored by Spaceweather.com reader JR Biggs, whose donation of $500 paid for the supplies neccesary to get the balloon off the ground. To say “thank you” for his contribution, we flew a birthday card for his daughter to the edge of space:

Happy Birthday to Autumn! She enjoyed watching a complete video of the flight when she turned 4 on Oct. 10th.

Readers, if you would like to support a research flight and send your birthday card, business logo, or other photo along for the ride, it only costs $500. Contact Dr. Tony Phillips to make arrangements.

The #1 movie in theaters right now is The Martian, a film adaptation of Andy Weir’s eponymous book. It tells the heart-pounding story of fictional astronaut Mark Watney, who is stranded on Mars and ultimately rescued by the crewmates who had inadvertently left him behind. To survive long enough to be rescued, Watney has to “science the hell out of” a very tricky situation: he grows food in alien soil, extracts water from rocket fuel, dodges Martian dust storms, and sends signals to NASA using an old Mars rover that had been buried in red sand for some 30 years.

It’s a thrilling adventure told with considerable accuracy—except, perhaps, for one thing. “While Andy Weir does a good job of representing the risks faced by Mark Watney stranded on Mars, he is silent on the threat of radiation, not just to Mark but particularly to the crew of the Hermes as they execute a daring rescue mission that more than doubles their time in deep space,” says Dr. Ron Turner, Distinguished Analyst at ANSER, a public-service research institute in Virginia.

Space radiation comes from two main sources: solar storms and galactic cosmic rays. Solar storms are intense, short-lived, and infrequent. Fortunately for Mark, there weren’t any during his mission. He dodged that bullet. However, he and his crewmates could not have avoided cosmic rays. These are high-energy particles that arise from supernovas, colliding neutron stars, and other violent events happening all the time in the Milky Way. They are ever-present, 24/7, and there is no way to avoid them. So far, NASA has developed no effective shield against these sub-atomic cannon balls from deep space. “Doubling a nominal spacecraft shielding thickness only reduces the GCR [galactic cosmic rays] exposure by a few percent,” notes Turner.

In the movie, Watney is actually safer than the crew of the Hermes. Turner explains: “The radiation exposure is significantly less on the surface of Mars. For one thing, the planet beneath your feet reduces your exposure by half. The atmosphere, while thin, further reduces the dose. The dose rate on Mars, while high, is only about 1/3rd of that on the Hermes.”

The biggest threat from cosmic radiation exposure is the possibility of dying from radiation-induced cancer sometime after a safe return to Earth. NASA’s radiation limits today are set to limit this life-shortening risk to less than three percent. Taking into account many factors, such as the phase of the solar cycle and the number of days the crew spent in deep space and on the surface of Mars, Turner has calculated the total dose of cosmic rays absorbed by Watney (41 cSv) and the crew (72 cSv). “cSV” is a centi-Seivert, a unit of radiation commonly used in discussion of human dose rates.

There is considerable uncertainty in how these doses translate into an increased risk of cancer. Turner estimates the added risk to Watney as somewhere between 0.25% and 3.25%. For members of the crew, the added risk ranges from 0.48% to 7.6%. The high end of these ranges are well outside NASA safety limits. The crew especially could be facing medical problems after their homecoming.

Post-flight cancer is not the only problem, however. “There is some additional concern that sustained radiation exposure could lead to other problems that manifest during the mission, instead of years afterward. Possible examples include heart disease, reduced immune system effectiveness, and neurological effects mimicking the symptoms of Alzheimer disease.”

As far as we can tell, none of these things happened to the crew of the Hermes. It’s just as well. They had enough trouble without cosmic rays. For the complete details of Turner’s analysis CLICK HERE (pdf).

05 Nov. 2015: Spaceweather.com and the students of Earth to Sky Calculus regularly fly helium balloons to the stratosphere to measure cosmic rays. For the past six months, May through Oct. 2015, they have been taking their radiation sensors onboard commercial airplanes, too. The chart below summarizes their measurements on 18 different airplanes flying back and forth across the continental United States.

The points on the graph indicate the dose rate of cosmic rays inside the airplanes compared to sea level. For instance, the dose rate for flights that cruised at 40,000+ feet was more than 50 times higher than the dose rate on the ground below. No wonder the International Commission on Radiological Protection (ICRP) classifies pilots as occupational radiation workers.

Cosmic rays come from deep space. They are high energy particles accelerated toward Earth by distant explosions such as supernovas and colliding neutron stars. Astronauts aren’t the only ones who have to think about them; flyers do, too. Cosmic rays penetrate deep inside Earth’s atmosphere where airplanes travel every day.

Cosmic Rays are modulated by solar activity. Solar storms and CMEs tend to sweep aside cosmic rays, making it more difficult for cosmic rays to reach Earth. Low solar activity, on the other hand, allows an extra dose of cosmic rays to reach our planet. This is important because forecasters expect solar activity to drop sharply in the years ahead as we approach a new Solar Minimum. Cosmic rays are poised to increase accordingly.

The plot, above, tells us what is “normal” in 2015. How will it change as the solar cycle wanes? Stay tuned for regular updates.

Approximately once a week, Spaceweather.com and the students of Earth to Sky Calculus fly “space weather balloons” to the stratosphere over California. These balloons are equipped with radiation sensors that detect cosmic rays, a surprisingly “down to Earth” form of space weather. Cosmic rays can seed clouds, trigger lightning, and penetrate commercial airplanes. Our measurements show that someone flying back and forth across the continental USA, just once, can absorb as much ionizing radiation as 2 to 5 dental X-rays. Here is the data from our latest flight, Oct. 11th:

Radiation levels peak at the entrance to the stratosphere in a broad region called the “Pfotzer Maximum.” This peak is named after physicist George Pfotzer who discovered it using balloons and Geiger tubes in the 1930s. Radiation levels there are more than 80x sea level.

Note that the bottom of the Pfotzer Maximim is near 55,000 ft. This means that some high-flying aircraft are not far from the zone of maximum radiation. Indeed, according to the Oct 11th measurements, a plane flying at 45,000 feet is exposed to 2.77 uSv/hr. At that rate, a passenger would absorb about one dental X-ray’s worth of radiation in about 5 hours.

Hey thanks! The cosmic ray research described above is 100% crowd-funded. Our Oct. 11th balloon flight was made possible by a generous donation of $500 from Spaceweather.com reader Vicki Brown. To say thanks, we flew Vicki’s parents, Betty and Earl, to the edge of space:

“I am so happy to help the young scientists, and it is cool to see my folks in the stratosphere!” says Vicki.

Readers, have you ever wanted to send a loved one to the stratosphere? You can make it happen by sponsoring a cosmic ray research flight. Contact Dr. Tony Phillips for details.